查找完成时，AVPlayer显示加载指示器

import AVKit

class ViewController: UIViewController {
    var player: AVPlayer?
    var playerViewController: AVPlayerViewController?

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建AVPlayer对象
        let videoURL = URL(string: "https://example.com/video.mp4")
        player = AVPlayer(url: videoURL!)
        
        // 创建AVPlayerViewController对象并设置player属性
        playerViewController = AVPlayerViewController()
        playerViewController?.player = player
        
        // 在视图中显示AVPlayerViewController
        addChildViewController(playerViewController!)
        view.addSubview(playerViewController!.view)
        playerViewController!.didMove(toParentViewController: self)
        
        // 监听AVPlayer的status属性，当为.readyToPlay时表示已加载完成
        player?.addObserver(self, forKeyPath: "status", options: .new, context: nil)
        
        // 显示加载指示器
        showLoadingIndicator()
        
        // 开始加载媒体资源
        player?.play()
    }

    // 监听AVPlayer的status属性变化
    override func observeValue(forKeyPath keyPath: String?,
                               of object: Any?,
                               change: [NSKeyValueChangeKey : Any]?,
                               context: UnsafeMutableRawPointer?) {
        if keyPath == "status" {
            if player?.status == .readyToPlay {
                // 隐藏加载指示器
                hideLoadingIndicator()
            }
        }
    }
    
    // 显示加载指示器
    func showLoadingIndicator() {
        let activityIndicator = UIActivityIndicatorView(style: .gray)
        activityIndicator.center = view.center
        activityIndicator.startAnimating()
        view.addSubview(activityIndicator)
    }
    
    // 隐藏加载指示器
    func hideLoadingIndicator() {
        view.subviews.filter { $0 is UIActivityIndicatorView }.forEach { $0.removeFromSuperview() }
    }
    
    deinit {
        player?.removeObserver(self, forKeyPath: "status")
    }
}